How much ciggarette smoke is too much?

im 17 weeks pregnant now and i live in a house where 5 people smoke, i used to but quit after knowing about my baby. i cant stand the smell of the smoke it makes me vomit but they don't care as its their house and don't care about their un born grandchild's health. i know the smoke can be harmful but how much is too much and what are the effects that it may be having on my baby?